College of Optometry Faculty Proceedings, Presentations, Posters, Speeches, Lectures, etc.

Title

Directional Bias Of Neurons In Visual Area 2 (V2) Of Strabismic Monkeys

Format

Poster

Conference Title

Society of Neuroscience Annual Meeting

Organization/Association/Group

Society of Neuroscience

Location

San Diego, California / November 10-15. 2001

Publication Date / Copyright Date

11-11-2001

Abstract

Strabismisc humans and monkeys are known to exhibit monocular naso-temporal asymmetries in visual tracking and pursuit eye movements. The neural basis for this anomaly is a matter of debate. In this study, we tested the hypothesis that these oculomotor asymmetries are associated with similar motion processing anomalies in visual cortex. The single unit activity of V2 neurons was recorded from 3 anesthetized and paralyzed monkeys that were reared with surgically-induced convergent strabismus in one eye. All monkeys were behaviorally tested for their monocular and binocular capacities prior to the neurophysiological experiments. During the recording experiments, we measured the responsiveness of individual units to 24 directions of stimulus movement. The preferred stimulus direction and the magnitude of the directional response bias were determined by a vector summation method. The sharpness of orientation tuning functions was also measured. We found no clear signs of naso-temporal asymmetries in direction tuning functions. However, the directional bias of V2 neurons for the deviating eye were lower and their orientation bandwidths were wider than those dominated by the non-deviating eye or normal control units. Thus, the oculomotor asymmetries in strabismic monkeys may be more closely associated with the reduced direction/orientation tuning of V2 neurons rather than an obvious asymmetry in the directional properties of V2 neurons.

Disciplines

Optometry

Keywords

extrastriate cortex, directional monkey

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